1. Field of the Invention
This invention relates to a method and a system for registering a domain or domains which can be used in domain management designed to protect data representative of or related to, for example, copyrighted or licensed contents and services.
2. Description of the Related Art
Throughout this specification, the word “content” means, for example, a home movie, a motion picture, a television program, an audio visual stream, a music tune, or a computer game program.
It is known that a server provides data representative of or related to copyrighted or licensed contents and services of various types to user's machine on a fee-charging or free-of-charge basis, and a user is permitted to use the contents and services through the user's machine. In this case, protecting the contents and services against illegal use thereof is important.
A typical management method is designed so that a contents provider gives permission for the use of contents to a selected machine or machines only, and the contents can be used through the machine or machines having the permission.
There is a known management method in which a plurality of machines are assigned to a domain, and a contents provider gives permission for the use of contents to the domain, that is, the machines assigned to the domain. Therefore, the contents can be used through each of the machines assigned to the domain.
Japanese patent application publication number 2002-169726 discloses a system in which information processing machines are separated into groups. Different group keys are assigned to the groups, respectively. A same group key is stored in each of machines in one group. In the system of Japanese application 2002-169726, each content is encrypted with a content key. In the case where an encrypted content is requested to be transmitted from one machine, a related content key is encrypted with a group key for a group having the present machine. Then, the encrypted content and the encrypted content key are transmitted from the present machine. Each of other machines in the group same as that having the present machine can decrypt the encrypted content key with the group key, and then decrypt the encrypted content with the decrypted content key. Therefore, each of these machines can use the original content. On the other hand, machines in groups different from the group having the present machine can not decrypt the encrypted content key. Thus, these machines can not use the original content.
Japanese patent application publication number 2004-120736 discloses a group formation managing system designed to fix the range of a group and allow contents to be used freely among devices in the group. The system of Japanese application 2004-120736 comprises registered member devices, a new member device, and a group managing device. Each of the registered member devices holds common secret information peculiar to a related group. The new member device sends the group managing device a request for registration with the group. The group managing device receives the request from the new member device, and decides whether or not the current number of registered member devices in the group is less than a limited number equal to a maximum number of registered member devices in the group. When it is decided that the current number of registered member devices in the group is less than the limited number, the group managing device registers the new member device with the group and then outputs the common secret information to the newly registered member device. The newly registered member device receives and holds the common secret information. When a content is to be used, the group managing device authenticates all member devices in the group according to the common secret information. The group managing device delivers the content only to each of member devices about which the authentication is successful. Therefore, it is possible to prevent the content from being used by member devices not holding the common secret information, that is, member devices not registered with the group.
In the system of Japanese application 2002-169726, each machine is required to obtain and store a group key. Japanese application 2002-169726 does not disclose a change in the grouping of machines. Specifically, Japanese application 2002-169726 does not disclose a case where machines in one group are newly added to another group. Japanese application 2004-120736 teaches the addition of a new member device to a group. However, Japanese application 2004-120736 does not disclose a case where machines in one group are newly added to another group.